Disposable absorbent pads come in a wide variety of shapes and sizes, however, all generally employ a liquid impermeable barrier sheet coated or supplied with an adhesive attachment region.
This adhesive attachment region has traditionally been coated with a hot-melt adhesive which is protected by a release liner. The release liner is left in place to protect the adhesive from contamination or from transfer to adjacent incontinent pads or sanitary napkins or packaging materials in the package prior to use, and is removed by the user prior to attachment of the article, e.g., a sanitary napkin or adult incontinent pad, to the fabric undergarment of the user.
Hot melt adhesives based on styrene block copolymers, i.e., SIS, SBS, SEBS, SEPS, etc., or other polymers like polyolefins, for use as positioning adhesive with absorbent articles have been widely used due to the ease of applying the adhesive to desired substrates and their good positioning properties to cotton. However, with increasing trends in the market towards more fashionable undergarments made from microfibre fabrics, which give silky, stretchy and good fitness-feeling, positioning adhesives must be able to bond microfibre fabrics, as well as other fabrics, in addition to cotton, and keep the absorbent articles in position without leaving residual adhesive on the undergarment following removal of the absorbent article.
Conventional hot melt positioning adhesives, however, do not bond to microfibre fabrics well. While higher tack positioning adhesives have been developed to improve bonding to microfibre fabrics, such adhesives bond too strongly to cotton. Bonding differences observed when using conventional adhesive on different fabrics, e.g., either too little bonding to microfibre fabrics or too aggressive bonding to cotton/nylon fabrics, are unacceptable to the end users of absorbent articles.
Another concern with the use of conventional positioning adhesives is that when a more breathable PE film is used as a back sheet, low molecular ingredients of the adhesive tend to migrate into the breathable film due to the absorbency of the breathable film. This results in staining of the breathable film and significantly reduces the bonding performance of the positioning adhesive on the absorbent articles. In addition to positioning performance being significantly affected (peel can drop by 80% of its original peel value), staining is easily observed on the absorbent product by the end user and is seen as a defect in the goods.
Yet another problem encountered with the use of conventional positioning adhesives is that performance is adversely affected when the articles comprise fragrances or lotions.
There is a need in the art for a disposable absorbent article comprising a non-staining hot melt adhesive with long term stable bonding stability, and for positioning adhesives with good bonding to different fabrics and, ideally, similar bonding to different fabrics under different use conditions, and for positioning adhesives that are fragrance and lotion resistant. The current invention addresses this need in the art.